Such an oscillatingly driven power tool is known from DE 10 2010 046 629 A1. In that case, a motor, by means of its motor shaft, directly drives an eccentric coupling drive, which converts the rotating driving motions of the motor shaft into an oscillatory motion that is converted, by means of a planetary gearing, into an oscillatory output motion of a tool spindle having an opposite direction of rotation.
Such an arrangement enables a tool spindle to be driven in a rotationally oscillating manner about its longitudinal axis, the tool spindle being drivable at a frequency in the desired range of approximately 5000 to 30000 l/min and with a swivel angle in the range of approximately 0.5° to 7°, depending on the driving speed of the motor, the transmission ratio of the planetary gearing, and the eccentricity and lever arm of the eccentric coupling drive.
Moreover, owing to the motion reversal effected by the planetary gearing, the vibration associated with the transmission is kept to a very low level.
However, the relatively large amount of noise generated and the wear susceptibility of the transmission may be considered to be disadvantageous.
In some cases, as an alternative to the use of toothed gearings, belt drives have also become known in the prior art for driving a tool spindle in the case of hand-held tools.
Thus, for instance, DE 43 42 986 C2 discloses the driving of a random-orbit sander by means of a belt drive that, by means of deflection rollers, converts the rotary motion of the drive motor into a rotary motion of an output shaft that extends at an angle in relation to the motor shaft and drives a random-orbit disc.
The use of a belt drive in connection with a sanding appliance is also known from US 2012/0080206 A1. In that case, however, the belt drive is used only to drive a suction extraction device.
Common to the aforementioned belt drives, however, is that they are only ever used to transmit a rotary motion.
Additionally known, from EP 0 337 303 A2, is a drive device for a saw blade, in which a connecting rod, operated by an eccentric pin of a motor shaft, is used to drive in oscillation a rocker arm that is mounted on one side. Fastened to the free end of the rocker arm is a tensioned band, provided as a transmission means, which serves to drive a saw tool.
This is not a belt drive in the conventional sense, however, but merely a cable drive, which serves to transmit the driving motion of a rocker arm, driven in an oscillatory manner, directly to a saw blade fastened to the cable or band.